1. Field of the Invention
This invention relates to a joint structure of a metal member and a ceramic member, and a method of producing the same.
2. Description of Related Art
At present, an electrostatic chuck is used for attracting and holding a semiconductor wafer in a transportation of the semiconductor wafer, film forming processes such as exposure to light, chemical vapor deposition (CVD), sputtering and the like, or steps of micromachining, cleaning, etching, dicing and the like. As a substrate for the electrostatic chuck, dense ceramics have been watched. Particularly, a corrosive halogen type gas such as ClF.sub.3 or the like is frequently used as an etching gas or a cleaning gas in an apparatus for the manufacture of the semiconductor. Furthermore, the substrate for the electrostatic chuck is desired to have a high thermal conductivity for rapidly heating and cooling the semiconductor wafer at a holding state. And also, it is desired to have a thermal shock resistance so as not to cause the breakage of the substrate due to a rapid temperature change. In this connection, a dense aluminum nitride, alumina and the like have a high corrosive resistance against the aforementioned corrosive halogen type gas.
Moreover, a susceptor provided with a high frequency electrode therein for generating plasma is put into practical use in the field of semiconductor-manufacturing apparatus. Even in the field of such an apparatus for generating high frequency power, a metal electrode is embedded in the substrate of aluminum nitride, alumina or the like.
In these apparatuses, it is necessary that the metal electrode is embedded in the ceramic substrate of aluminum nitride, alumina or the like and electrically connected to an external connector for supplying electric power. However, such a connecting portion is exposed to heat cycle of extremely high and low temperatures in an oxidizing atmosphere or further in a corrosive gas atmosphere. Even in such bad conditions, therefore, the connecting portion is desired to hold a high joint strength and a good electrical connection over a long period of time.
The inventors have already proposed a technique of manufacturing a ceramic heater, an electrostatic chuck or a high frequency electrode device used in the semiconductor-manufacturing apparatus, wherein a hole is made by machining in a substrate of aluminum nitride, silicon nitride or the like, and a metal electrode in the inside of the substrate is exposed from the hole, and a cylindrical fitting is inserted into the hole, and a top face of the metal fitting is brazed to the metal electrode (Japanese Patent Application No. 7-21657).
However, it has been confirmed that this technique has still the following problems. Namely, there are some cases that a given joint strength and electrical conductivity can not be ensured and hence the yield is lowered. For example, when the top face of the cylindrical metal fitting is brazed to the bottom face of the housing hole formed in the ceramic substrate, there may be caused a case that a sufficient amount of a brazing material is not retained in a joint portion of the housing hole because the brazing material extremely rises toward the side of the metal fitting through wetting. For this reason, it tends to lower a strength when stress is applied to the metal fitting.